In ALD applications, typically two gaseous precursors are introduced into the ALD reactor in separate stages. The gaseous precursors effectively react with the substrate surface, resulting in deposition of a single atomic layer. The precursor stages are typically followed or separated by a purge stage that eliminates the excess precursor from the surface of the substrate prior to the separate introduction of the other precursor. Therefore an ALD process requires alternating in sequence the flux of precursors to the surface of the substrate. This repeated sequence of alternating surface reactions and purge stages between is a typical ALD deposition cycle.
Particulate matter can be exposed to a condition in which a fluidized bed is formed in a vessel under conditions that cause the particulate matter to act in a fluidic manner. This is usually achieved by the introduction of pressurized gas through the particulate matter.
When providing coating to particulate matter with an ALD process problems arise since the coating should be applied all around the particulate matter and the particulate matter easily agglomerates.